Telephone trunk-circuit



(No Model.) A' l J. J. OCONNELL. TELEPHONE TRUNK GIRGUIT.

No. 587,226. Patented July 27, 1897.

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PATENT JOSEPH J. OCONNELL, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE AMERICAN BELL TELEPHONE COMPANY, OF BOSTON, MASSACHUSETTS.

TELEPHONE TRUNK-CIRCUIT.

SPIECIFICATION forming part of Letters Patent No. 587,226, dated uly 27, 1897.

Application led February l1, 1897. Serial No. 622,970. (No modeLl Y To all whom t may concern:

Be it known that I, JosEPHJ. OCoNNELL, residing at Chicago, in the county of Cook and State of Illinois, have invented certain lmprovements -in Telephone Trunk-Circuits, of

which the following is a specification.

The present invention relates to trunk-circuits employed in telephone central offices or exchanges, and is arranged so that the opio erators at both ends are enabled to display vcall and disconnecting signals at the keyboard of the other.

I have illustrated the invention in connection with atrunk and signaling circuit extendr 5 in g between abr-anch telephone-exchange and a main exchange,.but it is applicable to any trunk-circuit and is essentially as follows: At the branch operators table the trunk-circuit terminates in a plug, which when not in zo use is located in a plug-seat containing a switch, and its Withdrawal therefrom or replacement therein acts to open or close at one point two local circuits at the home end, in

' one of which is a call-signaling device and v in the other a similar disconnecting-signal,

While a polar relay, operated mainly from the other end of the trunk, by its armature opens and closes the said local circuits at a second point'. There are means, shown as two 3c batteries with opposite poles to line, for sending currents of diverse direction through the circuit and a call-key at the operators board. At the main or distributing switchboard the trunk-line terminates in a plug-socket, by means of which andan answering-plug two local circuits, one having a call-signal and the other a-disconnecti'ng-signal, are closed at one point, while a polar relay operated from the branch operators keyboard controls' the 4o local circuits each at another point. Means for sending call or signaling currents of both directions are at this switchboard also, and are shown as comprising two call-batteries with opposite poles to line and a call-key. Normally the local signal-circuits at both ends of the trunk-conductors are closed at' one point and open at another point.

At both stations or switchboards glow-lamps are preferably employed as signal-receiving appliances.

The operation of sending signals from each end is much the same. The branch operator in calling the distributing or main switchboard operator presses a key which sends, say, a plus current to the trunk-signal line operating the polarized relay at the main station to close a local circuit and display the call lamp-signal. At the same time the home relay operates to close the call-signal circuit and open the disconnecting-signal circuit at 6o the points it controls, butthe signal in the former circuit is not manifested, because the trunk-plug has been withdrawn from its seat and inserted in the switch socket or jack of the calling-substation, and by such withdrawal has opened at another point the circuit of the said signal.

When the operator at the main station inserts the answering-plu g into the trunk-jack, the call-signal local circuit is opened and the 7o lamp extinguished. At the same time the home disconnecting-signal circuit isA closed in the jack. Upon ascertaining the call the second or associate plug is inserted in the jack of the called substation.

Upon the termination of conversation either operator may first disconnect-say that the branch operator removes the trunk-plug and replaces it in its seat. The switch of such plug-seat is thereby actuated and a momen- 8o tary minus current flows over the signal-Wire,

a portion of which operates the home-relay, opening the call lamp-circuit at the point controlled thereby and closing the disconnecting lamp-circuit. The remainder of the current operates the relay at the main station, which at the points it controls opens the call lampcircuit and closes the disconnecting lamp-signal circuit lighting the same. The operator there then takes down the plugs, opening the 9o disconnecting-signal circuit inthe jack and thus extinguishing the lamp and at the samel time closing the call-signal circuit.

If the operator at the main station Was to give the disconnecting-signal,the plugs would be taken down, thereby opening the home disconnecting-signal circuit and closing the callsignal circuit in the trunk-jack and sending a momentary minus current to 'the branch oice and operating the relay there to close Ioo against the lever g.

the disconnecting-signal circ uit and light the lamp, which circuit will again be opened when the trunk-plug is replaced in its seat.

The operator at the main station can call the branch station by closing a key and sending a plus current, which will cause the relayarmature at the said branch station to close the call-signal circuit and light the lamp.

It will be noticed that the disconnect-ing signal at each end of the trunk is operated by a momentary or short-d uration current. This eifect is produced by similar peculiar and novel devices located at the branch station in the plug-seat switch and at the main station in the tiunlejack, which are automatically operated by the insertion and withdrawal of the trunkpl ug in or from its seat and of the answering-plug in or from the trunlcjack, all of which will be described in detail hereinafter.

In the drawings which illustrate the in vention, Figure lis a diagram of a trunkl and signaling line between branch and main telephone-stations, and Fig. 2 is a section of a plug-seat switch employed therein.

L is the trunk talking-circuit, consisting of conductors a l), the former terminating at the sleeve of plug K at the branch station X and at spring 40 of jack J at the main station Y. The latter conductor connects with spring 42 of jack J, and, by means of contact 14 and spring of key A and wire 16, to tip of plug K.

c is an associated signaling-wire for the said trunk-circuit and connects to ground G, through controlling-signals S and R and their local circuit-s 2l and 53, polarized relay C, and wire 18 at one end, and by polarized relay D, which controls t-he signals E and N and their local circuits and 36, and wire 83 to ground lf2 at the other end.

T is a plug-seat switch consisting of a table e, of insulating material, with a hole in one end in which is inserted a tube fwith a flange p at its bottom and having a slot o cut in one side thereof, into which projects the lower end of lever g, pivoted at 7L.

j is a dust-proof casing secured to the under side of the table e, the bottom 7 being nonconducting and holding the springs 4, 7, and 8. The former spring extends through a slot in the table c, between the contacts 5 and 6, and is provided with a pin i', which rests The springs 4 and 7 are separated by insulation and move as one, the top ot' the latter spring being recurved and provided with a contact and insulatingtip A is a leverpivoted at m, its upper end playing between the tips and the contact 50, and its lower end rests against the pian.' The spring 8 is provided with a pin 26, which rests in a slot 5l on the side of the lever A.

The contact 6 is connected by wire 2l to lamp l S, which is arranged to constitute a disconnecting signal and minus contact of relay C, and contact 5 by wire 53 to the callsignal lampR and plus contact. The armature 2O is connected by wire 9 with wire 18. The trunk signal-wire c is connected with spring 7 by wire 17, and spring4is connected with spring 8 by wire 22 and with battery M and ground G by wire 2S.

Battery B is connected from ground G by wire 24 to contact-stop 12 in key A, (whose spring 10 connects by wire 1 with conductor CL,) and by spring l1, which moves with spring lO, and wire 2 with signal-wire c.

The spring 28 in jack .l at Yis recurved and provided with a contact von its tip and an insulatingstriker 5G, against which the lower end ot the lever A-` presses. The lever A2 is pivoted at G0 and has a notch opposite its pivot in which the pin 26 on the spring 25 presses. The spring 25 is connected by wire ISO to the battery Hand ground G2. The spring 38 is separated from spring 40 by insulation 39, and both move together, the former be ing connected by wire 31 with battery I and gro und. A pair of looping-plugs P and P2 are shown, and substation-circuits are represent ed by the line-jacks J2 and J3 at the ends, rcspectively, of the trunk-circuit.

The signal-wire c between the stations X and Y may be omitted and the trunk-conductors a and b used as one conductor by putting suitable resistance-coils 44 between them and connecting the ends of wire c to the center thereof by wires 45, as shown in dotted lines and as well understood by those skilled in the art.

In the operation of the invention, assuming that a call `has been made by substation represented by jack J 2, the branch operator raises the plug K and inserts it in the jack J2 and receives the call in the usual manner and then presses in the key A. The removal of the plug permits the springs 4 and 7 to move to the lett until the former strikes the contact G and closes the disconnecting-signal local circuit `21 at that point,ithe insulated tip z moving the top of the lever A to the leftuntil its lower end strikes the pin n. As the said top of the lever is forced over thc pin 26 holds it insuch position, where, however, it is not in contact with the point 50 on the spring 7. The key A is `then pushed in, breaking connection between contact 14 and spring 15 and bringingspring 11 into contact with stop 12, whereby a part of the plus current from battery B is caused to flow over the branch conductor 2 and signal-wire c through relay D at station or switchboard Yand wire 33 to ground G2. This causes the armature .'34 to close the local circuit of the .signal E by way of ground G2, wire 31, battery l, spring 38 of jack J, wires 36, 57, and 33, signal E, and relay-armature to ground, andthe said call lamp-signal E is lighted, manifesting the signal. A portion of the plus current divides at point 3 and Hows over wires c and 18, through relay C to, ground G, causing the armature 2O to close the call-signal local circuit 555 at that point of said circuit which it controls; but the signal is not ex- TOO IIO

hibited, because theI same circuit has previously been opened at by the movement of the spring 4 consequent on the withdrawal of the plug K from its seat. The main operator inserts answering-plug P2 into jack J and,

ascertaining the call, inserts the lother plug- P into the called-for jack J 3. The insertion of the plug P2 into jack J forces spring 3S away from contact 41 into contact with pin 37, opening the call-signal circuit and extinguishing lamp E and closing the disconnecting-signal circuit at that point. At the same time the spring 28 forces the upper end of lever A2 into contact with pin n, the lower end approaching contact 55, but not touching the same. The pin 26 on spring 25 holds the lever A2 in its new position.

A disconnecting-signal can be given from either end. For instance, the branch operator removes the plug K from jack J2 and inserts it in the plu g-seat, where it operates the plugseat switch by forcing the lever g and pin t' to the right, which causes the contact 50 on the spring 7 to strike the lever A and force it over into position shown at X, where it is held by the spring S. While the spring 7 is momentarily in contact with the lever A', minus current flows from battery M by spring 8, lever A', spring '7, wires 17 and c, relay D, and wire 33 to ground G2, which causes the relay-armature to go to the right and close the disconnecting-signal circuitI and light the lamp N at Y. The main-switchboard operator thereupon withdraws the plug P2, which causes lthe spring 3S to open the disconnectingsignal circuit and close the call-circuit in the jack J. At the same time the spring 28 draws the lever A2 into position Ashown at Y, and a momentary minus current is sent from battery H over the signal-wire, but will not operate the armature of relay C.

If the disconnecting-signal is sent from the main station Y by the withdrawal of plug P2 from jack J the momentary minus current just referred to will operate the relay C and cause its armature to close the disconnectingsignal circuit and light the lamp S, as will be readily seen, and when the plug K is inserted in its seat the local circuit of the disconnecting-signal is broken at 6, and the momentary minus current which iiows through the relay C from battery M will not operate its armature, that being already in the position to which by the influence of such current it would be attracted.

A call-signal can be sent from the main station Y when the plug K is in its seat at the branch station X by pressing key k, thus sending a plus current from battery I through lthe relay C, which causes its armature to close the call-signal circuit and light the lamp R.

Much annoyance has been experienced in plug-seat switches because of the collection of dust between the contacts of the springs, and to avoid this I inclose the springs in the device described herein in the casing j. It is evident that the lever g may be dispensed with and the pin i extend through the opening o into the socket, but the construction shown is preferable.v

I claim- 1. In a telephone system, the combination of a trunk-circuit between two switchboards,

lan associated signal-circuit, and two local cirwhereby the display of either signal at either switchboard is determined in part by the condition of the switch connections, and in part by the operation of the polar relay at the said switchboard, such operation being responsive to signaling-currents transmitted from the other switchboard. v

2. In a telephone system, a trunk-circuit between two switchboards, provided at one:

end with a switch-plug terminal, and at the other with a switch-socket or spring-j ack terminal, an associated signal-circuit, a plugseat for said plug-terminal, two local circuits at eachfswitchboard, and independent call and disconnecting signals also at each switchboard included in the'said local circuits respectively; combined with a polar relay in the signal-circuit at each end thereof, and circuit-controllin g devices in the said switchsocket and plug-seat actuated in each case-by the insertion and withdrawal of the switchplug,`the said. relay and circuit controlling devices at each point being adapted and arranged to conjointly control the said two local circuits at such point; and means at each switchboard for transmitting currents of both direction or polarity over'the signal-circuit for the operation of lthe polar relay at the other, substantially as described.

3. A trunking system comprisinga trunkcircuit between two telephone-switchboards, terminating at both switchboards in'suitable plug and spring-jack connecting devices; an associated signal-circuit; two local signalingcircuits at each switchboard, containing a call-signal and a disconnecting-signal respectively; a polar relay at each switchboard included in the main signaling-circuit, and con; trolling at one point the continuity of the ltwo local circuits at such switchboard; and

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4. In a telephone system the combination with a trunk-circuit extending between two switchboards, an associated signal-` circuit, two local circuits at each end of said trunk and signal circuit-s, and independent call and disconnecting signals also at each end contained in the said two local circuits respectively, of a polar relay in the signaling-circuit at each end thereof, and switch connections in the trunk-circuit at each end thereof, the said relay and switch connections at each point controlling jointly the said two local circuits at such point, and means for sending currents of both directions over the signaling-circuit from either end thereof tothe other 5 whereby the display of the signals at either station is made dependent partly upon the operation of its polar relay by a current sent from the other station, and partly on the condition of its own trunk-switch connections, substantially as described.

5. A telephonie conversation and signaling circuit provided at both ends with two lampsignals in independent local circuits, a polarized relay adapted to alternately open one and close the other of said local circuits and vice versa, at one point, according to the direction of a signaling-current in the main signaling -circuit, two batteries with opposite poles to line, and means `for uniting the said line to either battery; the said main circuit being also provided at one end only with a switch-plug terminal, and aplug-seat switch, and at the other end only with a spring-jack or switch-socket terminal; the said plug-seat switch at one end, and spring-jack at the other being both adapted when associated with switch-plugs to alternately open one and close the other of their respective local circuits, and vice versa, at a second point,

be actuated by the movement of the other contact-spring to reverse its position, said spring being adapted to make electrical contact with the lever, substantially as described.

7. In a trunking system between two eX- changes a combined talking and signaling circuit provided at each exchange with a sig'- naling battery and key, a polarized relay, a battery and two lamp-signals in independent local circuits, and means for connecting with a substation-circuit consisting at the first exchange, of a plug and a seat-switch therefor; and at the second exchange ot' a spring-jack and connecting cord and plugs; whereby when the said plug is restored t0 the seatswitch or the looping-plug is withdrawn from the said spring-jack a momentary current is caused to iiow 'over the circuit and light a disconnecting lampsignal at the other end.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, this lith day of February, 1897.

JOSEPH J. OCONNELL.

Witnesses ARTHUR D. WHEELER, WILLIAM MATHIESEN. 

